All of the patents cited throughout this specification are hereby entirely incorporated herein.
Quaternary ammonium compounds are well known as complexing agents for anionic dyes. For example, U.S. Pat. No. 5,059,244, to King, discloses an aqueous solution of anionic dyes and an ethoxylated triethanolamine. This composition is useful as an ingredient within ink formulations and as an agent for temporarily tinting textile fibers; however patentee neither teaches nor fairly suggests removing any excess inorganic salts. Quaternary ammonium compounds have been disclosed as useful auxiliary agents for printing on fiber materials. For example, U.S. Pat. No. 3,785,767, to Hildebrand, discloses a pad-steaming process for the continuous dyeing and printing of fiber material with a formulation containing anionic dyes and amine salts. Other pertinent teachings of include U.S. Pat. No. 4,563,190, to Topfl, which discloses a dyeing assistant formulation for anionic dyes containing quaternary ammonium compounds that contain at least one basic nitrogen atom to which are attached at least one polyglycol ether chain; U.S. Pat. No. 4,935,033, to Mosimann et al., which discloses a dyeing method for natural polyamide fibers using reactive dyes and a dyeing assistant agent containing a quaternary ammonium compound; and U.S. Pat. No. 4,369,041, to Dvorsky et al., discloses a technique for printing textiles involving exposing the textile to the action of quaternary ammonium compounds before or during the dyeing or printing with acid dyes. Furthermore, Aston et al., U.S. Pat. No. 5,403,358, discloses a pretreatment composition for ink jet which comprises a quaternary ammonium compound and a reactive dye. Such anionic dyes and quaternary ammonium compounds also find application in other areas, for instance: U.S. Pat. No. 4,459130, to Helling et al., discloses a dye preparation which is consisted of an acid dye and a basic carrier which contains quaternary ammonium or phosphonium groups; and U.S. Pat. No. 5,266,077, to Auten et al., discloses a method for tinting a hydrophilic contact lens through the action of a quaternary ammonium compound as a dye complexing agent.
Anionic dyes, in particular acid dyes (i.e., those containing sulfonic or carboxylic acid moieties) provide desirable and beneficial coloring characteristics to many different types of substrates. However, it has proven very difficult to incorporate such beneficial dyes, with acceptable coloring performance, within certain media, such as waxes, polyolefins, polyurethanes, hydrocarbons, and the like. The polarity (hydrophilicity) of such acid dyes is sufficiently high so as to prevent long-lasting dyeing or even any coloring at all within such media. Attempts have been made to utilize more hydrophobic solvent dyes (and other less polar dyes having no acid groups) as colorants for thermoplastics, and the like; however, such a procedure has also proven too disadvantageous since solvent dyes can easily migrate within and out of the aforementioned desired media. There exists a need then to produce an acid dye which possesses the requisite degree of hydrophilicity effectively to bond with and remain within media such as polyolefins, and the like (as noted above).
It has been found that the complexation of an anionic dye with a quaternary ammonium compound and the subsequent removal of substantially all the excess unwanted salts formed during such a reaction produces a solid colorant complex which possesses the highly desired and necessary properties as delineated previously. It has been found that substantially salt-free anionic dye/quaternary ammonium colorant complexes, provide a colorant with a high coloring capacity within many different media with a very low potential for extraction. When placed in a complexing solution, the anionic dye and the quaternary ammonium show a great affinity for one another such that upon disassociation with their respective cations and/or counter ions, the complexation of the dye and quat drives the formation of the unwanted salts comprised of the free cations and counter ions. Once these unwanted salts are formed, they are easy to remove through filtration or extraction techniques. Such a salt removal ensures the dye and quat will remain in a complex together rather than potentially reacting with unwanted free cations and/or counter ions upon disassociation within the dye solution. Thus, the desired properties are obtained with a greater amount of the dye/quat complex and a much lower amount of unwanted residual salt.
Although a great deal of interest has been demonstrated within the area of anionic organic dyes and/or quaternary ammonium compounds as coloring or treating agents for myriad substrates, there is no disclosure of a substantially salt-free solid complex of the two compounds which provides extremely good non-migration within certain media as well as excellent coloring characteristics, and the like, wherein the quaternary ammonium compound has an average molecular weight of below about 900. The closest art, U.S. Pat. No. 4,468,883, to Podder, which teaches anionic dye/polystyrene ion exchange/possible quat colorant particles, discloses quaternary ammonium compounds having, at the absolute lowest level, average molecular weight of 1,000, with patentee's preferred quats having average molecular weights of 10,000 or above. There is thus a great need within the dye and/or colorant art for such types of improvements associated with relatively inexpensive materials and processes as provided by the inventive colorant complexes.
Basically, then, the simplest manner of practicing the invention is first determine the desired anionic dye for its shade, lightfastness, thermal stability, and the like, for the subject substrate to be colored; second, select the appropriate quaternary ammonium compound, with a molecular weight of below about 900, for the subject substrate based on the necessarily required physical properties such as migration, uniform dispersion, solubility, washfastness, and the like; third, react the two compounds together to form a solid colorant; and last, remove the unwanted salts formed from the cation of the dye and the counter-ion of the quat.